Combination switch contact and rivet



MILL- 19 z0 In W. D. KIGHT COMBINATION SWITCH CONTACT AND RIVET Filed April 50, 1948 m H 4 5 I Z, w. w W 5 5 E 1| WNW f Va 5 E v.9 fi

llllllll Patented Aug. 21, 1951 COMBINATION SWITCH CONTACT AND RIVET )William D. Kight, Cincinnati, Ohio Application April 30, 1948, Serial No. 24,261

1 Claim.

Small switches or circuit breakers are used for various purposes where fairly heavy electric currents must be made and interrupted many times in a single second, an instance of such use being in the breaker points in the ignition system of an automobile engine. The cooperating contact pieces in these devices are usually tungsten discs brazed or otherwise fastened to supporting elements. In order, among other things, to reduce arcing and to provide ventilation in at least one of the contacts effective during the breaking of the circuit, I have in my prior Patent No. 2,339,996 divided one of the discs of each cooperating pair into a plurality of sections, at least superficially. This results in keeping down the temperature of the contacts to a certain extent, but faults due to overheating, erosion and pitting at the faces of the divided discs to some extent still remain.

The object of the present invention is to improve the construction, operation and maintenance of switches or breakers very substantially beyond the results attained through the type of slotting disclosed in the aforesaid patent.

In carrying out my invention, I mount a contact disc on the head of a rivet that can easily be afiixed to an arm, plate or other support; ease of attachment of the rivets being brought about b making their stems hollow.

A further object of the present invention is to utilize a slotted contact together with the hollow stem of the supporting rivet in a manner to achieve a greatly increased ventilating and cooling effect during the use of a switch or breaker embodying the improved construction.

When serious wear and erosion, due to heavy arcing, occurs on one contact piece, the resistance to flow of current increases and a ridge appears on the other contact piece. A further object of the present invention is to prevent the development of such a ridge and to reduce the resistance to current flow by providing what may be termed a walking edge of fresh tungsten when under such conditions severe arcing, and consequent deterioration of a contact face, is apt to take place.

The various feature of novelty whereby the present invention is characterized will hereinafter be pointed out with particularity in the claim, but, for a full understanding of the invention and of its objects and advantages, reference may be had to the following detailed description taken in connection with the accompanying drawing, wherein:

Figure 1 is a side or edge view of one end of an arm element having one of my improved contact units attached thereto; Fig. 2 is a top plan view of the structure appearing in Fig. 1; Fig. 3 is a section on line 33 of Fig. 2; Fig. 4 is an axial section through the rivet after the contact disc has been integrated therewith, prior to slotting; Fig. 5 is a plan View of the blank structure of Fig. 4; Fig. 6 is a view similar to Fig. 3, illustrating a modification; Fig. 7 is a view looking upward from line 7-7 of Fig. 6; and Fig. 8 is a view similar to Figs. 3 and 6, showing a still further modification.

Referring to Figs. 4 and 5, 10 is an iron rivet comprising a stern I I and a head I2 which is preferably square or of some other shape that permits the rivet to be accurately held in a predetermined position relative to a slotting tool. Rising from the head is a low cylindrical projection I3. The stem is in the form of a sleeve whose bore M extends through element I2 and far enough up into part I3 to leave only a thin top wall I5. It will be understood that the rivet is shown on a greatly enlarged scale, the proportions being the same, however, as in a typical commercial device having a stem .156 inch in external diameter and a combined thickness of head members I2 and I3 of about .060 inch. It will thus be seen that bore I4 is so large that the wall thickness in the tubular stem is less than one sixth as great as the external diameter of the stem; that wall I5 is less than one half as thick as the wall of the stem; while the width of the slots I9 is even less than the thickness of the thin wall I5.

A tungsten contact piece in the form of a disc I6 is set on top of the rivet head and is brazed thereto along line H. The blank thus created is then slotted in a manner to cut clear through the actual contact piece and through wall I5 into the cavit within the rivet; one or more slots extending diametrically across the tungsten disc. In Figs. 1-3 of the drawings there are two such slots I9 and 26, respectively, arranged at right angles to each other and dividing the disc into four sections. It will be seen that these slots are continued downward for the few thousandths of an inch necessary to cut entirely through wall I5 of the rivet and produce therein slots 2I and 22, respectively.

The finished combined contact piece and rivet is secured in its position of use on an arm 23 or other supporting member by inserting the stem through a hole 24 in such member; the free end of the stem being then swaged laterally to create a flange 25 that cooperates with rivet head I2 to clamp the supporting member between the flange and the head.

In Figs. 6 and '7 the slots are cut at an angle to the face of the contact, the preferable angle being about 40. In top plan view these slots, I9 and 20*, have the same appearance as the slots l and in Fig. 2; but each recedes from the axis of the rivet as it penetrates farther and farther below the said face; until, finally, they appear far off center as slots 2 l and 22 opening into cavity M as shown in Fig, 7.

In Fig. 8 the structure is the same as in Fig. 3, except that the upper end of the cavity I l in the rivet l0 is not flat but is dome shaped. In forming this cavity there may be used a punch having a tapered end provided with longitudinal wings or vanes that create vertical slots 26 branching out from the dome of the cavity and extending up to the level of the top of the latter. The slots that are cut through the tungsten disc are in registration with the slots 26 and open into the latter. In other words, the cuts coming down through the top do not meet any thicker wall at the upper end of the cavity in the rivet than is the case in the first form described. However, there is more metal directly under the tungsten disc than there is in the first form; providing a somewhat more solid support for the disc.

All of the units illustrated possess the characteristic of being ventilated, because there is a free passage extending completely through the entire structure; the large diameter of the cavity in the rivet permitting rapid escape of gases generated when arcing takes place at the face of the contact and the entrance of cooling air. Furthermore, each unit is factory made and, because of the character of the rivet, can easily be installed by makers of equipment requiring such devices. It will also be seen that the total height of each rivet and its contact piece, is small when mounted on the support, so that it can be used where little space is available.

The construction shown in Figs. 6 and 7 has the added advantage that as the face of the contact piece deteriorates from the effects of arcing and suffers from erosion, the slots in effect travel crosswise of the face of the contact piece; providing walking edges that constantly present fresh tungsten surfaces for cooperation with a cooperating contact.

This not only cuts down resistance to flow of current, but practically eliminates the formation of ridges on a cooperating contact. It should also be noted that this feature is of value in other types of slotted contact pieces, as, for example, those disclosed in my aforesaid Patent No. 2,339,996, wherein the slots are all closed on their under sides.

While I have illustrated and described with particularity only a Single preferred form of my invention, together with a few slight modifications, I do not desire to be limited to the exact details thus illustrated and described, but intend to cover all forms and arrangements that come within the definitions of my invention constituting the appended claim.

I claim:

A circuit making and breaking element comprising a headed rivet and a contact piece overlying and fixed to the head, said rivet having a tubular stem wherein the bore has a dome-shaped upper end that extends up to within a few thousandths of an inch from the top face of the head, the dome-shaped portion of the bore being provided with slot-like branches opening laterally therefrom and reaching to within said few thousandths of an inch from the top face of the head, and said contact piece and the head containing slots that extend across a transverse dimension of the same, through the thickness of the contact piece and into registration and communication with said slot-like branches of the bore.

WILLIAM D. KIGHT.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 1,052,987 Weed Feb. 11, 1913 1,146,881 Jeifries July 20, 1915 1,223,143 Briggs Apr. 17, 1917 1,653,823 Pudelko Dec. 27, 1927 1,841,428 Barrows Jan. 19, 1932 2,018,073 Laise Oct. 22, 1935 2,072,112 King Mar. 21, 1937 2,339,996 Kight Jan. 25, 1944 2,521,561 Batcheller Sept. 5, 1950 

